text: class Queue(object):
      def __init__(self):
          self.items = []
  
      def isEmpty(self):
          return not bool(self.items)
  
      def enqueue(self, item):
          self.items.insert(0, item)
  
      def dequeue(self):
          value = self.items.pop()
          if value is not None:
              return value
          else:
              print("Queue is empty.")
  
      def size(self):
          return len(self.items)
  
      def peek(self):
          if self.items:
              return self.items[-1]
          else:
              print("Queue is empty.")
  
      def __repr__(self):
          return self.items.__repr__()
  
  class Deque(Queue):
      def enqueue_back(self, item):
          self.items.append(item)
  
      def dequeue_front(self):
          value = self.items.pop(0)
          if value is not None:
              return value
          else:
              print("Deque is empty.")
  
  
  
  
  
  